#include #include using namespace std; using i64 = long long; class range {private: struct I{int x;int operator*(){return x;}bool operator!=(I& lhs){return x struct Modint { static const Modint* none; // *modint::none long long x; Modint(void) { x = 0; }; Modint(long long a) { x = (a%mod+mod)%mod; }; Modint(string s) { x = 0; for(char c : s) { (x *= 10) += (c - '0'); x %= mod; } // if(!x) { x = mod; } }; static Modint* noneInstance(void) { Modint* res = new Modint(); res->x = -1; return res; } bool is_none(void) { return x == -1; } Modint operator + (const Modint a) { return Modint(*this) += a; } Modint operator - (const Modint a) { return Modint(*this) -= a; } Modint operator * (const Modint a) { return Modint(*this) *= a; } Modint operator * (const long long a) { return Modint(*this) *= (a%mod+mod)%mod; } friend Modint operator * (const long long a, const Modint& b) { return Modint(b) *= (a%mod+mod)%mod; } Modint operator +=(const Modint& a) { if((x+=a.x)>=mod) { x-=mod; } return *this; } Modint operator -=(const Modint& a) { if((x-=a.x)<0) { x+=mod; } return *this; } Modint operator *=(const Modint& a) { (x*=a.x)%=mod; return *this; } Modint operator *=(const long long a) { (x*=(a%mod+mod)%mod)%=mod; return *this; } /* a++ */ Modint operator ++(int) { Modint old; old.x = x; if((x+=1)>=mod) { x-=mod; }; return old; } /* ++a */ Modint operator ++(void) { *this += 1; return *this; } /* a-- */ Modint operator --(int) { Modint old; old.x = x; if((x-=1)<0) { x+=mod; }; return old; } /* --a */ Modint operator --(void) { *this -= 1; return *this; } bool operator ==(const Modint& a) const { return x == a.x; } bool operator ==(const long long a) const { return x == (a%mod+mod)%mod; } bool operator !=(const Modint& a) const { return !(x == a.x); } bool operator !=(const long long a) const { return x != (a%mod+mod)%mod; } int intvalue(void) const { return (int)x; } Modint pow(const long long n){ Modint res = 1; long long p = x; for(long long i=n; i>0; i>>=1) { if(i & 1) { res *= p; } (p *= p) %= mod; } return res; } }; template const Modint* Modint::none = Modint::noneInstance(); const int mod = 1000000007; using modint = Modint; const int non = 0, ke1 = 1, ke2 = 2, paa = 3; vector> dp; int main(void) { int n; scanf("%d", &n); dp.assign(2, vector(4)); dp[non][0] = 1; for(int i : range(n)) { int cur = i & 1, nxt = !cur; dp[nxt][ke1] += dp[cur][non] + dp[cur][paa]; dp[nxt][ke2] += dp[cur][ke1]; dp[nxt][paa] += dp[cur][ke1] + dp[cur][ke2]; dp[cur].assign(4, 0); } modint res = accumulate(dp[n&1].begin(), dp[n&1].end(), modint(0)); printf("%d\n", res.intvalue()); return 0; }